Tesis Doctoral/PHD

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Browsing Tesis Doctoral/PHD by Author "Alvarado Martínez, Andrés Omar"

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    Comparative assessment of a mountain river flow resistance – 1D-: sensitivity and prediction using data-based approaches
    (Universidad de Cuenca, 2022-11-21) Cedillo Galarza, Juan Sebastián; Alvarado Martínez, Andrés Omar
    Mountain -rivers are, by far, the most challenging case to model because of its bed characteristics and their energy dissipation mechanisms depending on its irregular morphology. Resistance, roughness, or friction parameter are equivalent terms. It plays an important role in 1-D open channel models to estimate different variables. Moreover, this parameter contains all the dissipative processes in a mountain river, and it is usually valued through field measurements, existing different methodologies to estimate it. Consequently, it is essential to determine which methodology is the most adequate to predict it. The resistance parameter determined in field is not always the same as the one used in a hydrodynamic model. In this thesis; cascades, plane bed, and step-pool has been studied in the Quinuas river (Ecuador). “Non-dimensional hydraulic geometry equations” (NDHG) were the best option to predict velocity in all the mountain river reaches. The parameters of NDHG varies depending on the author, therefore a methodology based on some field measurements to estimate the NDHG parameters was developed. The differences between model and field resistance coefficient depends on the morphology and flow magnitude. A machine learning technique using the system physics was develop providing optimal results to predict water depths and to calibrate resistance parameter.
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    Hydrodynamic assessment of different UASB reactor’s influent distribution systems to improve granulation
    (Universidad de Cuenca, 2022-05-17) Cisneros Ramos, Juan Fernando; Alvarado Martínez, Andrés Omar
    Wastewater treatment systems are implemented to remove wastewater pollutants before discharge into receiving water bodies. Wastewater can negatively affect the ecosystem of the receiving water body if proper treatment is not conducted. Despite its importance, small coverage of wastewater treatment systems has been achieved worldwide mainly due to the related high construction and operating costs. According to the Food and Agriculture Organization, about 80% of the world’s wastewater generation is discharged into the environment without any treatment, especially in low-income countries. Anaerobic biological wastewater treatments could be an answer to reduce treatment costs. Anaerobic technologies offer advantages over competing technologies such as reduced land footprint, small reactor volume, reduced excess sludge production, and the ability to recover energy through methane capture. The most widespread anaerobic technology worldwide is the Upflow Anaerobic Sludge Blanket (UASB) reactor. The UASB reactor uses an upward flow to produce granular sludge capable of treating high organic loads. Although there is extensive information on the microbiology of these granules and their efficiency in treating different wastewater qualities, further research is required to better understand the relationship between granule formation and reactor hydrodynamics. Flow hydrodynamics, almost entirely controlled by the reactor's Influent Distribution System (IDS), is key to consider during the UASB reactor’s design since it modules the substrate distribution inside the reactor and the formation of stagnant and short-circuited zones. The IDS role is critical, especially during the reactor's start-up stage when the granular sludge starts to form. This thesis aimed to advance our understanding of the flow hydrodynamics impact on the operation and efficiency of the UASB reactor during its startup stage. The research was divided into two main stages. The first stage was dedicated to physically modeling the reactor using a Froude dynamic similitude scaled reactor and developing an automated tracer testing system. This system allowed us to determine the importance of controlling the test water's conductivity, temperature variation, and surface tension during the tracer tests. The second stage was devoted to numerically modeling the hydrodynamics of the UASB reactor using computational fluid dynamics (CFD) simulations. Initially, the research focused on finding the turbulence closure model that best reproduced the reactor’s hydrodynamics. Thus, CFD simulations were conducted using the realizable k-epsilon model to assess the potential volume of granule generation for IDS configurations commonly used in the literature. The simulations confirmed that the IDS configuration recommended by the design guidelines has a high performance in reducing stagnant and short-circuited zones. This research proposed a novel IDS configuration that generated a granulation volume 22% larger than the recommended IDS configuration, potentially reducing UASB reactor start-up time. The research demonstrates the potential of using physical and numerical techniques as a basis for the model-based design approach to solve problems specific to UASB reactors, an approach that could be extrapolated to other types of reactors.
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    Towards an efficient and functional design of constructed wetlands systems for wastewater and sludge treatment in high altitude tropical regions
    (Universidad de Cuenca, 2024-09-05) Arévalo Durazno, María Belén; Alvarado Martínez, Andrés Omar
    The treatment of wastewater and sludge through decentralised natural systems, such as the French System, represents a sustainable and effective strategy. This system uses two stages of vertical flow constructed wetlands (VFCWs) to treat raw wastewater, eliminating sludge generation. Despite its extensive use in France, its application in Latin America, particularly in high-altitude Andean regions, has been limited. The main objective of this thesis was to investigate the feasibility of applying the French System for the treatment of domestic wastewater and septic sludge under the climatic conditions of the Andean Region, at 2500 meters above sea level, through a pilot study in Cuenca, Ecuador. Results showed that VFCWs can continuously handle extreme hydraulic loads of diluted wastewater, with proper feeding and resting periods, reducing the required treatment area and minimizing sludge accumulation. It was also determined that septic tanks remain common in both urban and rural areas, making the treatment of fecal sludge necessary. By using VFCWs for this type of sludge, it was observed that the use of multiple beds allows for adequate treatment, and that retaining the percolate for seven days significantly improves the removal of COD and TS without increasing the treatment area. The French System shows great potential for use in areas with climates similar to the Andean region for the treatment of domestic wastewater and septic sludge.